1. Field of the Invention
The present invention relates a new pigment composition and, more particularly, to a pigment composition useful as a coloring material such as paint, printing ink, or a synthetic resin colorant in which a phosphonic ester compound containing a residue of hydraxy carboxylic acid and/or hydroxy ester thereof is used as the pigment dispersant or flushing agent.
2. Description of the Prior Art
In the conventional process for producing paints and printing inks, lecithin, which is one of phospholipids, has been used both as a dispersant for dispersing a pigment into a paint vehicle or printing ink varnish, and as a flushing agent for flushing the aqueous filter cake into an oil vehicle or oil varnish.
Being a natural phospholipid, lecithin is liable to oxidation and rancidity which lead to deterioration and putrefaction. Thus there has been a demand for a dispersant or flushing agent which is stabler and better than lecithin.
In view of the above-mentioned drawbacks of the conventional dispersant or flushing agent and in order to develop a new compound which is compatible with vehicles and varnishes and also with pigments and is useful as a pigment dispersant, the present inventors carried out a series of researches which led to the finding that a phosphoric ester obtained by reacting a hydroxy carboxylic acid and/or hydroxy ester thereof with phosphoric acid exhibits outstanding properties and effects required for pigment dispersants. The present invention was completed based on this finding.